Syrian rebels killed at least 11 people, including civilians, in an attack on a checkpoint west of the city of Homs on Saturday that official state media described as a massacre.

Most of those killed were Christians, activists and residents said. Some were from the National Defence Army, a militia which fights alongside President Bashar Assad's soldiers, and others were civilians, they said.

"Terrorists today committed a massacre, killing 11 people ... in Homs countryside," the state news agency SANA quoted an official as saying.

The Syrian Observatory for Human Rights said rebel gunmen had attacked the checkpoint, killing five militia fighters and six civilians, including two women. It said the rebel fighters had also sustained losses.

A resident who visited the site of the overnight attack said he saw the remains of a destroyed checkpoint and two civilian cars nearby, whose passengers may have been caught up by chance in the fighting.

He said the checkpoint had been used as an artillery base to bombard the rebel town of Hosn, about 2 km (1 mile) away, which lies below the towering Crusader castle Crac des Chevaliers.

Many Christians fleeing the violence in Homs city over the past two years have settled in the Christian villages around the area where Saturday's attack took place.

Some have joined the pro-Assad forces, fearing for their future were the president to be toppled by rebel forces increasingly led by radical Islamist brigades, some with links to al-Qaida.

More than 100,000 people have been killed in Syria's civil war, which grew out of a 2011 uprising against 40 years of dynastic rule by the Assad family, and nearly 2 million more have fled the country as refugees.

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